Physostigmine, see Eserine, above.
Pilocarpine, C„H,,,X,O; a semi-fluid alkaloid soluble in alcohol, ether, and chloroform; gives a green coloration with strong sulphuric acid and potassium bi-ehromate. It is one of the active principles of pilocarpus. or jaborandi, the leaflets of Pilocarpus sclloanus Engler, or of Pilocarpus jaborandi Holmes.
Piperidinr, C,II„N; a liquid alkaloid produced by the decomposition of piperine, a substance found in pepper.
Piperinc, CwHi9NO3; melting point, 12S° C.; soluble in hot water and in chloroform; with strong sulphuric acid it gives a yellow color that changes to brown, then to a greenish brown. It is found in plants of the natural order Piper acca., and is one of the chief constituents of ordinary black pepper.
Quinidinc, melting point, 168° C.; soluble in chloroform, less so in alcohol and ether; sparingly soluble in water; its solution turns the plane of polarized light to the right. It is found in einchona bark.
Quinine, + 311,0; melts in its water of crystallization at 57° C., loses its water at 100°, then melts again at 177° C.; soluble in alcohol, ether and chloroform, sparingly soluble in water; its solutions turn the plane of polar ized light to the left. It is found in cinchona bark.
Solanine, C4211,3NO;5; melting point, 235° C.; it may be extracted from its alkaline solutions by means of chloroform; with strong sulphuric acid it gives an orange coloration that turns a brownish red. It is found in bittersweet (woody nightshade), the young branches of Solanum dulcamara Linne.
Strychnine. ,N,0,; melting point, about 264° C.; soluble in chloroform and in hot alco hol; sparingly soluble in water and in ether. It gives a pretty display of colors with strong sul phuric acid and a grain of potassium bi-chro mate. It is found in plants of the natural order Loganiaccw, and is usually obtained from mix vomica.
Thebaine, or Paramorph-ine, melt ing point, 193° C.; soluble in alcohol and chlo roform; gives, with strong sulphuric acid, a dark-red coloration which turns yellow. It is found in opium.
Theinc, see Caffeine, above.
TheobrOM inc, sublimes without melting at 290° C.; sparingly soluble in the or dinary solvents; may be extracted from an alka line solution by means of chloroform. On eva poration with chlorine-water a brown residue is obtained that turns purple if a little ammonia is added. It is found in cacao beans.
Veratrine, a mixture of two iso meric alkaloids; melting point, 155° C.; soluble in alcohol, ether, and chloroform; gives a red coloration if heated with sulphuric or m with funning hydrochloric acid. It is found in the seed of Asogresa officinalis Lindley.
The extraction of an alkaloid from the plant in which it occurs is often a matter of consid erable difficulty. The volatile alkaloids may be obtained by distilling the plant or vegetable product with water and lime (o• caustic soda) ; the liquid distilling over is neutralized with sul phuric acid and evaporated to dryness; the sul phate of the alkaloid may then be dissolved out of the residue by means of a mixture of alcohol and ether. To extract a non-volatile alkaloid,
the plant is macerated and treated with a dilute solution of some acid in ordinary alcohol; the solution thus obtained is rendered alkaline by the addition of soda, and the alkaloid set free is either directly obtained in the form of a pre cipitate, or else may be extracted from the alka line solution by mea-ns of ether, chloroform, or some other solvent that does not mix with water. Such processes, however, usually yield not one single, but mixtures of two or more al kaloids, and those contaminated with large quantities of other organic substances, which often render the isolation of a single alkaloid in the pure state very difficult..
As to the chemical constitution of alkaloids, very little is as yet known. It has been found, however, that most of these substances are ter tiary aromatic bases, and that by far the greater number of them contain one or more methoxy groups, GCH„ linked to a benzene nucleus. The chemical relationship of the alkaloids to pyri dine, quinoline, and uric acid, has been mentioned above. Most alkaloids have a powerful physio logical action even if employed in very small quantities. The action of certain alkaloids is, however, at least partly antagonistic to the ac tion of certain others. For this reason one alka loid may sometimes be employed to relieve the poisonous effect of another alkaloid, though it may itself be a violent poison. The antagonism of morphine and atropine is of considerable value in cases in which a subcutaneous injection of morphine is indicated: the cardiac depression, indigestion. and constipation, usually caused by morphine, may be prevented by injecting sim ultaneously a trace of atropine.
, The alkaloids are sometimes spoken of as vegetable bases, natural organic bases, or veg etable alkaloids. The latter name is applied to them in contradistinction to the animal alka loids, or ptomaines, that are formed during the putrefaction of animal products. Like the vegetable alkaloids, the ptomaines are highly poisonous nitrogenous bases, and they resemble the vegetable alkaloids both in their chemical properties and in their physiological action. See PTOMAINES.
BIBLIOGRAPHY. Pictet, La constitution chintBibliography. Pictet, La constitution chint- ;glue des alcaloidcs tYgOaux (second edition, Paris, 1897; German translation, Berlin, 1891) ; Dupuy, Alcaloides (Brussels, 1887-89) ; Schmidt, dic Erforschung der Konstitution and (lir Vcrsuche zur Synthesc wichtiger Pilanzenal kaloidr (Stuttgart, 1900) ; Briihl, Die Pflanz-en alkaloide (Brunswick, 1900). The most impor tant alkaloids are described in some detail under their special names.